A graphite-based disc dry cleaning method for silicon-based nitride epitaxy

Abstract

The application discloses a graphite-based disc dry cleaning method for silicon-based nitride epitaxy, and comprises the following steps: vacuum preheating and primary cleaning, heating to a first temperature interval in a vacuum environment, and cleaning by inputting inert gas and changing pressure; high-temperature deep cleaning, heating to a second temperature interval, cleaning by inputting mixed gas of inert gas and reducing gas and continuously changing pressure; pressure drop cooling transition, cooling to a third temperature interval, cutting off the reducing gas, only inputting inert gas and maintaining pressure change cleaning; vacuum and cooling termination, stopping inputting inert gas, keeping vacuum, cooling to a fourth temperature interval, filling inert gas and cooling to room temperature. The application utilizes the "breathing effect" generated by pressure pulse and the synergistic effect of high-temperature chemical reduction, forces the reaction gas to deeply enter the SiC coating micro-pit of the graphite-based disc, efficiently decomposes and discharges the strong adhesion deposits such as AlN and GaN, and can clean the deposits while avoiding damaging the silicon carbide coating.

Description

Technical Field

[0001] This invention relates to the field of semiconductor epitaxial manufacturing equipment technology, and more specifically, to an efficient dry cleaning method for graphite-based disk surface deposits generated during silicon-based nitride epitaxy processes in metal-organic chemical vapor deposition (MOCVD) related equipment. Background Technology

[0002] With the widespread application of third-generation wide-bandgap semiconductor materials, represented by gallium nitride (GaN), in 5G radio frequency communication, new energy vehicle electronic control, and high-efficiency optoelectronics, epitaxial growth technology has become a core driving force for industry development. Among them, silicon (Si) substrate-based nitride epitaxial technology has become the mainstream technology route for high-power power electronic devices due to its compatibility with mature CMOS processes, large-size wafer manufacturing capabilities (8-inch / 12-inch), and significant cost advantages.

[0003] However, unlike sapphire or silicon carbide substrates, silicon substrates exhibit significant lattice mismatch (approximately 17%) and a large difference in thermal expansion coefficients (approximately 54%) with nitride materials. To overcome the resulting enormous stress and suppress cracking, silicon-based epitaxial processes must introduce thick and complex superlattice buffer layers (such as AlN / AlGaN superlattices) and high-temperature nucleation layers. This means that during MOCVD growth, the graphite substrate not only has to withstand more intense temperature fluctuations but also needs to be exposed to higher concentrations of aluminum (Al), gallium (Ga), and ammonia (NH3) sources. This results in the easy formation of complex, extremely hard, and difficult-to-remove mixed deposits (such as AlN, GaN, and their polycrystalline composites) on the SiC protective coating on the substrate surface.

[0004] Among existing cleaning methods, offline wet etching (pickling) is not only cumbersome and generates hazardous waste, but strong acids can also easily damage the SiC coating on the surface of the graphite substrate, shortening the life of the substrate. On the other hand, conventional in-situ high-temperature baking is inefficient at removing chemically stable aluminum-containing deposits, and prolonged extreme high-temperature baking will accelerate the aging of the substrate itself.

[0005] Therefore, given the unique characteristics of silicon-based nitride epitaxy, developing a dry cleaning technology that can efficiently decompose complex deposits without damaging the SiC coating is a key technical challenge that urgently needs to be addressed in the current field of silicon-based nitride epitaxy. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy. This method aims to overcome the problems of existing wet etching processes that easily damage the silicon carbide (SiC) coating on the graphite-based disk surface, the difficulty of removing residues in pits using mechanical polishing, and the low efficiency of traditional high-temperature baking methods. The cleaning method provided by this invention not only has a simple process flow and causes no damage to the disk itself, but also provides excellent deep cleaning results, solving the problems of high cleaning costs and short disk lifespan in existing technologies.

[0007] To solve the above-mentioned technical problems or achieve the above-mentioned objectives, the present invention adopts the following technical solution: According to the present invention, a dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy is provided, comprising the following steps: Vacuum preheating and primary cleaning: The graphite substrate is placed in a sealed furnace chamber, and the temperature inside the furnace chamber is raised to the first temperature range under vacuum. During this period, inert gas is introduced into the furnace chamber and pressure swing cleaning is performed. High-temperature deep cleaning: The temperature inside the furnace cavity is raised from the first temperature range to the second temperature range. During this period, a mixture of inert gas and reducing gas is introduced into the furnace cavity, and pressure swing cleaning operation is continuously performed. Pressurized cooling transition: The temperature inside the furnace cavity is cooled from the second temperature range to the third temperature range. During this period, the supply of reducing gas is cut off, and only inert gas is introduced while maintaining the pressure swing cleaning operation. Vacuum and cooling termination: When the temperature inside the furnace chamber drops to the third temperature range, the inert gas supply is stopped. Then, the furnace chamber is kept in a vacuum environment, and the temperature inside the furnace chamber is cooled from the third temperature range to the fourth temperature range. Subsequently, inert gas is introduced into the furnace chamber and cooled to room temperature.

[0008] In one embodiment of the present invention, the variable pressure cleaning operation includes cyclically performing air filling and air extraction steps, so that the pressure in the furnace cavity fluctuates alternately between a preset upper limit pressure and a lower limit pressure, wherein the upper limit pressure is 0.5 Torr-7 Torr, the lower limit pressure is 0.01 Torr-0.49 Torr, the duration of the air filling step is 3s-8s, and the duration of the air extraction step is 40s-90s.

[0009] In one embodiment of the present invention, the first temperature range is 200℃-400℃, the second temperature range is 1300℃-1450℃, the third temperature range is 800℃-950℃, and the fourth temperature range is 600℃-850℃.

[0010] In one embodiment of the present invention, the steps of vacuum preheating and primary cleaning further include: The temperature inside the furnace chamber was raised from room temperature to 30℃-50℃ while a vacuum process was performed simultaneously. Vacuuming was performed until the pressure inside the furnace reached 10. -1 Torr-10 -2 Torr, and raise the temperature to the target temperature within the first temperature range at a rate of 0.5℃ / min-5℃ / min. During this heating process, the pressure swing cleaning operation of the inert gas is initiated and maintained.

[0011] In one embodiment of the present invention, the high-temperature deep cleaning step further includes: The temperature inside the furnace cavity is gradually increased from the first temperature range to the target temperature in the second temperature range at a heating rate of 3℃ / min-15℃ / min. Maintain a constant temperature at the target temperature for 120 min–400 min. Throughout the heating and isothermal processes, a pressure swing cleaning operation of the mixed gas is continuously performed.

[0012] In one embodiment of the present invention, the step of pressure cooling transition further includes: The temperature inside the furnace cavity is cooled from the second temperature range to the third temperature range at a cooling rate of 5℃ / min-10℃ / min. During this period, the supply of reducing gas is cut off, and only inert gas is introduced. The same inert gas flow rate and pressure swing cleaning operating parameters as in the high-temperature deep cleaning step are maintained during this cooling period.

[0013] In one embodiment of the present invention, the step of terminating the vacuum and cooling process further includes: The temperature inside the furnace cavity is reduced from the third temperature range to the fourth temperature range at a cooling rate of 5℃ / min-10℃ / min. During this period, gas filling is stopped and gas is discharged to maintain the vacuum environment of the furnace cavity. After the temperature inside the furnace chamber drops below the lower limit of the fourth temperature range, inert gas is introduced into the furnace chamber to atmospheric pressure, and the temperature inside the furnace chamber is reduced to room temperature.

[0014] In one embodiment of the present invention, before performing vacuum preheating and primary cleaning, the furnace cavity is cleaned by inert gas replacement at least three times to reduce the oxygen content in the furnace cavity to below a safe threshold.

[0015] In one embodiment of the present invention, the inert gas includes N2, with a flow rate of 500 sccm-1500 sccm and a purity ≥99.9999%; the reducing gas includes H2, with a flow rate of 95 sccm-150 sccm and a purity ≥99.9999%; wherein in the high-temperature deep cleaning step, the volume ratio of N2 to H2 in the mixed gas is (5-15):1.

[0016] In one embodiment of the present invention, the diameter of the graphite substrate disk is 180mm-380mm and the skirt length is 50mm-65mm.

[0017] The technical solution provided by this invention has the following advantages compared with the prior art: This invention innovatively proposes a collaborative cleaning mechanism based on dynamic pressure field coupled with stepped temperature control. By cyclically executing "gas filling-gas extraction" variable pressure cleaning operations at each process stage, a high-frequency, large-amplitude sawtooth pressure waveform is constructed within the furnace cavity. The "breathing effect" generated by the pressure pulse forces reducing gas (H2) deep into the micron-level pits of the SiC coating on the graphite substrate disk, efficiently decomposing stubborn deposits such as AlN and GaN that are difficult to reach using traditional methods and expelling them with the airflow. This completely solves the technical bottlenecks of existing wet etching processes that easily damage the silicon carbide (SiC) coating on the graphite substrate disk surface and mechanical polishing methods that cannot remove microporous residues.

[0018] This invention achieves a high degree of balance between thorough cleaning and non-destructive treatment of the substrate. By precisely dividing four characteristic temperature ranges (200℃-400℃ low-temperature preheating, 1300℃-1450℃ high-temperature reduction, 800℃-950℃ pressurized transition, and 600℃-850℃ vacuum cooling), sufficient reaction energy is provided for the reduction and decomposition of Group III nitrides, while thermal stress shock and chemical corrosion are controlled within the safe threshold of the SiC coating. The substrate surface cleaned by the method of this invention is as smooth as new, and the coating is intact. The cleanliness and performance of the substrate after cleaning can be restored to near-new levels.

[0019] This invention significantly extends the service life of graphite substrates and reduces production costs. By avoiding strong acid corrosion and mechanical damage, and effectively preventing high-temperature oxidation and secondary sublimation contamination through pressurized cooling transition and vacuum cooling termination steps, this invention can extend the reusable service life of graphite substrates to over 260 furnace cycles, significantly reducing consumable costs in MOCVD epitaxial production compared to traditional cleaning methods. Furthermore, the entire process of this invention is dry, eliminating the use of hazardous chemicals such as strong acids and alkalis, thus eliminating hazardous waste emissions and aligning with the development direction of green manufacturing.

[0020] This invention achieves atomic-level cleanliness of the graphite substrate while perfectly protecting the integrity of the SiC coating through the synergistic effect of "pressure swing breathing effect" and "stepped temperature control". It significantly improves the uniformity and crystal quality of the epitaxial wafer, greatly extends the substrate life, and has outstanding advantages such as excellent cleaning effect, no damage to the substrate, high process safety, and good environmental protection. It has important industrial practical value for improving the yield of silicon-based nitride epitaxial products and reducing production costs. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0022] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0023] Figure 1 The flowchart illustrates a dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy provided in an embodiment of the present invention. Figure 2 A schematic diagram of the periodic pressure control process window for the dry cleaning method of graphite-based disks in an embodiment of the present invention is shown. Figure 3 A schematic diagram of the overall structure of the graphite substrate disk in an embodiment of the present invention is shown; Figure 4 The surface morphology of the graphite substrate disk before and after cleaning is shown in Figure (a), where Figure (b) is the surface morphology before cleaning and Figure (a) is the surface morphology after cleaning. Figure 5 The histograms of the probability density distribution of the dominant wavelength (WLD) of the epitaxial wafers obtained in Comparative Example 1 and Example 1 are shown in comparison. Figure 6 The diagram shows a comparison of the in-plane spatial distribution cloud maps of the effective region of PL intensity (INT) of the epitaxial wafers obtained in Comparative Example 1 and Example 1, where Figure (a) is Comparative Example 1 and Figure (b) is Example 1. Figure 7 A comparison graph showing the radial distribution trend of warpage of the epitaxial wafers obtained in Comparative Example 1 and Example 1 is shown. Detailed Implementation

[0024] To better understand the above-described objectives, features, and advantages of this disclosure, embodiments of this disclosure will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0025] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways than those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0026] like Figure 1As shown, an embodiment of the present invention provides a dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy, comprising the following steps: S1. Vacuum preheating and primary cleaning: The graphite substrate is placed in a sealed furnace cavity, and the temperature inside the furnace cavity is raised to the first temperature range under vacuum. During this period, inert gas is introduced into the furnace cavity and a pressure swing cleaning operation is performed. S2. High-temperature deep cleaning: The temperature inside the furnace cavity is raised from the first temperature range to the second temperature range. During this period, a mixture of inert gas and reducing gas is introduced into the furnace cavity, and the pressure swing cleaning operation is continuously performed. S3. Pressurized cooling transition: The temperature inside the furnace cavity is cooled from the second temperature range to the third temperature range. During this period, the supply of the reducing gas is cut off, and only the inert gas is introduced while maintaining the pressure swing cleaning operation. S4. Vacuum and Cooling Termination: When the temperature inside the furnace chamber drops to the third temperature range, the inert gas supply is stopped. Then, the furnace chamber is kept in a vacuum environment, and the temperature inside the furnace chamber is cooled from the third temperature range to the fourth temperature range. Subsequently, inert gas is introduced into the furnace chamber and cooled to room temperature.

[0027] The dry cleaning method for graphite-based disks provided by this invention constructs a complete cleaning mechanism from physical thermal desorption to chemical reduction etching by coupling staged temperature control with a dynamic gas pressure field. Utilizing the "breathing effect" generated by the variable pressure operation, it forces reactive gas into the micron-sized pits of the SiC coating on the graphite-based disk, efficiently decomposing and expelling aluminum (Al), gallium (Ga), and their nitride deposits deeply embedded within the SiC coating micro-pits, thus significantly improving the cleanliness of the disk surface.

[0028] In the above embodiments, the variable pressure cleaning operation includes cyclically performing air filling and air extraction steps, so that the pressure in the furnace cavity fluctuates alternately between a preset upper limit pressure and a lower limit pressure, wherein the upper limit pressure is 0.5 Torr-7 Torr, the lower limit pressure is 0.01 Torr-0.49 Torr, the duration of the air filling step is 3s-8s, and the duration of the air extraction step is 40s-90s.

[0029] In this embodiment, the present invention rapidly switches between gas filling and gas extraction to form a sawtooth-shaped pressure waveform within the furnace cavity, thereby establishing a strong aerodynamic shear force and concentration gradient on the surface of the SiC coating on the graphite substrate and inside the micro-pits, thus enhancing the mass transfer process. The present invention precisely controls the process parameters of the pressure swing cleaning operation within a timing window of 3s-8s for gas filling and 40s-90s for gas extraction, and a fluctuation range of upper pressure limit 0.5Torr-7Torr and lower pressure limit 0.01Torr-0.49Torr, enabling the construction of a sawtooth-shaped pressure waveform with both high amplitude and high frequency within the furnace cavity. This specific "fast filling, slow extraction" mode induces strong airflow shear force and transient pressure gradient on the surface of the graphite substrate and inside the micro-pits of the SiC coating. On the one hand, the transient high pressure during the gas filling stage forces the reducing gas to overcome the microporous diffusion resistance and penetrate into the bottom layer of the deposit; on the other hand, the long-term low-pressure environment during the gas extraction stage completely removes the decomposed gaseous products, thus generating a highly efficient "breathing effect" synergistic effect. This parameter combination not only enhances the mass transfer process, ensuring that stubborn deposits such as AlN and GaN hidden deep in micron-level pits are completely removed, but also avoids mechanical damage to the SiC coating caused by excessive airflow impact by optimizing the pressure fluctuation amplitude. It achieves atomic-level cleanliness while maximizing the protection of the surface integrity of the graphite substrate.

[0030] In the above embodiments, the first temperature range is 200℃-400℃, the second temperature range is 1300℃-1450℃, the third temperature range is 800℃-950℃, and the fourth temperature range is 600℃-850℃.

[0031] In this embodiment, the temperature range is set based on the thermal decomposition temperature thresholds of different types of deposits and the thermal performance boundaries of the SiC coating. In this embodiment, the present invention constructs a step-by-step synergistic mechanism from low-temperature physical desorption to high-temperature chemical reduction by precisely dividing the cleaning process into four characteristic temperature ranges. Specifically, the first temperature range of 200℃-400℃ utilizes the increased mean free path of molecules, combined with inert gas pulses, to achieve gentle desorption of water vapor and volatile residues; the second temperature range of 1300℃-1450℃ is precisely controlled within the thermal stability domain of the SiC coating, providing sufficient reaction energy for H2 reduction of highly stable nitrides such as AlN and GaN, while preventing ablation or phase transformation damage to the coating due to overheating; the third temperature range of 800℃-950℃ serves as a pressurized cooling transition section, effectively suppressing reverse adsorption or secondary sublimation of gaseous metal atoms due to supersaturation through continuous airflow pulsation; and the fourth temperature range of 600℃-850℃ isolates oxygen in a high-vacuum environment, preventing high-temperature oxidation etching. This synergistic design of stepped temperature zones enables the entire cleaning process to achieve atomic-level removal of deep, stubborn deposits while minimizing thermal stress impact, ultimately extending service life while restoring the mirror-like smoothness of the base plate.

[0032] In the above embodiment, step S1 of vacuum preheating and primary cleaning further includes: The temperature inside the furnace chamber was raised from room temperature to 30℃-50℃ while a vacuum process was performed simultaneously. Vacuuming was performed until the pressure inside the furnace reached 10. -1 Torr-10 -2 Torr, and raise the temperature to the target temperature within the first temperature range at a rate of 0.5℃ / min-5℃ / min. During this heating process, the pressure swing cleaning operation of the inert gas is initiated and maintained.

[0033] In this embodiment, the increased mean free path of molecules under low pressure, combined with inert gas rinsing, effectively removes water vapor and volatile organic compounds adsorbed on the substrate surface. The vacuum preheating and primary cleaning step S1 of this invention, through precise coordinated control of heating and evacuation, creates a clean initial interface for subsequent deep cleaning. Specifically, a vacuum is simultaneously evacuated to 10°C under a low-temperature environment of 30°C-50°C. -1 Torr-10 -2Torr utilizes the characteristic that the mean free path of molecules increases significantly under low pressure to efficiently desorb water vapor and volatile organic compounds adsorbed on the substrate surface without damaging the SiC coating. Subsequently, the temperature is slowly increased to the first temperature range at a rate of 0.5℃ / min-5℃ / min, combined with pressure swing cleaning using inert gas. This avoids carbonization or secondary adhesion of surface contaminants caused by excessively rapid heating, and the gentle airflow pulsation promptly removes desorbed impurities from the furnace chamber. This gradual treatment strategy of "extraction followed by blowing, slow heating" achieves atomic-level pretreatment of the substrate surface without introducing thermal stress, providing an ideal, pollution-free, and oxidation-free reaction interface for the subsequent high-temperature reduction reaction stage. This fundamentally ensures the thoroughness of the overall cleaning process and the integrity of the coating.

[0034] In the above embodiment, step S2 of high-temperature deep cleaning further includes: The temperature inside the furnace cavity is gradually increased from the first temperature range to the target temperature in the second temperature range at a heating rate of 3℃ / min-15℃ / min. Maintain a constant temperature at the target temperature for 120 min–400 min. Throughout the heating and isothermal processes, a pressure swing cleaning operation of the mixed gas is continuously performed.

[0035] In this embodiment, a reducing gas (e.g., H2) undergoes a high-temperature reduction reaction with the deposits, converting them into gaseous metal atoms or hydrides. High-temperature deep cleaning utilizes the principles of reaction thermodynamics and kinetics to effectively peel off highly adhesive deposits while ensuring the thermal stability of the SiC coating, thereby thoroughly cleaning the residues inside the microstructure of the graphite substrate disk. The high-temperature deep cleaning step of this invention achieves dual optimization of efficient removal of stubborn deposits and coating protection through precise control of the heating rate, isothermal window, and dynamic pressure field. First, a stepwise heating strategy of 3℃ / min-15℃ / min is adopted, ensuring the uniformity of the temperature field within the furnace cavity, avoiding microcracks in the SiC coating due to thermal shock, and gradually activating the decomposition reaction pathways of different deposits in different temperature zones. Subsequently, a long-term isothermal period of 120 min-400 min is maintained at the target temperature of 1300℃-1450℃, providing sufficient reaction time for H2 to reduce highly stable nitrides such as AlN and GaN, ensuring that deposits deeply embedded in the micro-pits are fully decomposed. Throughout the heating and isothermal processes, a continuous coupling of pressure-switching cleaning operations is employed. The "breathing effect" generated by the pressure pulses continuously replenishes the reaction interface with fresh reducing gas and promptly removes gaseous reaction products (such as Ga vapor), significantly reducing the inhibitory effect of product partial pressure on reaction equilibrium. This synergistic mechanism of "slow heating-long-term isothermal control-dynamic gas exchange" can thoroughly remove complex deposits while keeping the thermal ablation and chemical corrosion of the SiC coating within safe thresholds. This achieves an atomically clean surface while maximizing the lifespan of the graphite substrate.

[0036] In the above embodiment, step S3 of the pressurized cooling transition further includes: The temperature inside the furnace cavity is cooled from the second temperature range to the third temperature range at a cooling rate of 5℃ / min-10℃ / min. During this period, the supply of reducing gas is cut off, and only inert gas is introduced. The same inert gas flow rate and pressure swing cleaning operating parameters as in the high-temperature deep cleaning step are maintained during this cooling period.

[0037] In this embodiment, step S3 is designed to prevent gaseous metal atoms from undergoing reverse adsorption or secondary sublimation due to supersaturation during the cooling process, and to thoroughly purge the residual reaction byproducts out of the furnace cavity through continuous airflow pulsation.

[0038] Step S3, the pressurized cooling transition, effectively solves the problem of secondary contamination of gaseous products after high-temperature cleaning by precisely controlling the cooling rate and maintaining a dynamic airflow field. Specifically, a moderate cooling rate of 5℃ / min-10℃ / min avoids thermal stress damage to the SiC coating caused by excessively rapid cooling, while also preventing gaseous metal atoms from remaining on the substrate surface for extended periods due to excessively slow cooling. During this process, the same inert gas (e.g., N2) flow rate and variable pressure cleaning operating parameters as in the high-temperature deep cleaning stage are maintained. Continuous pressure pulsed airflow continuously flushes the furnace cavity, promptly removing reaction byproducts such as Ga vapor that may precipitate due to supersaturation during cooling, effectively suppressing secondary sublimation on the graphite substrate surface and in the micro-pits. This "constant current variable pressure, uniform cooling" transition strategy constructs a dynamic cleaning barrier between the high-temperature reaction zone and the low-temperature cooling zone, ensuring that the decomposed deposits are completely discharged from the furnace cavity, providing a clean and residue-free interface for the subsequent vacuum cooling stage, thereby guaranteeing the thoroughness and repeatability of the overall cleaning process.

[0039] In the above embodiment, step S4, which terminates the vacuum and cooling process, further includes: The temperature inside the furnace cavity is reduced from the third temperature range to the fourth temperature range at a cooling rate of 5℃ / min-10℃ / min. During this period, gas filling is stopped and gas is discharged to maintain the vacuum environment of the furnace cavity. After the temperature inside the furnace chamber drops below the lower limit of the fourth temperature range, inert gas is introduced into the furnace chamber to atmospheric pressure, and the temperature inside the furnace chamber is reduced to room temperature.

[0040] In this embodiment, when the temperature drops from the third temperature range to the fourth temperature range, the gas supply is completely stopped, the furnace chamber is evacuated to a vacuum and maintained in a vacuum environment. This step S4 utilizes the high vacuum environment to isolate oxygen, preventing the graphite substrate at high temperature from contacting trace amounts of oxygen and causing oxidation and etching, thereby protecting the mirror finish of the substrate surface.

[0041] In this embodiment, step S4 of the present invention, which terminates vacuum and cooling, achieves clean cooling while ensuring the integrity of the substrate surface through staged vacuum isolation and controlled gas filling. Specifically, the temperature is reduced from the third temperature range to the fourth temperature range at a rate of 5°C / min-10°C / min, during which a high vacuum environment is maintained. The oxygen-free properties of the vacuum effectively prevent the graphite substrate at high temperature from contacting with residual trace oxygen and causing oxidation and etching, thereby completely protecting the mirror finish and stoichiometry of the SiC coating. After the temperature drops below the lower limit of the fourth temperature range (e.g., 850°C), inert gas is introduced into the furnace cavity to atmospheric pressure and the temperature is further reduced to room temperature. This avoids the efficiency being affected by slow vacuum radiation cooling in the low-temperature section and achieves uniform cooling through inert gas convection heat transfer, effectively suppressing thermal stress caused by excessive temperature difference. This segmented termination strategy of "high-temperature vacuum protection - low-temperature inert gas cooling" ensures that the substrate surface is not oxidized again after cleaning, while maintaining the thermal uniformity of the coating to the maximum extent, providing a key guarantee for the long-life application of graphite substrates.

[0042] In the above embodiment, before performing the vacuum preheating and primary cleaning step S1, the furnace cavity is cleaned by inert gas replacement at least three times to reduce the oxygen content in the furnace cavity to below the safe threshold.

[0043] In this embodiment, the present invention reduces the oxygen content below a safe threshold by performing inert gas replacement cleaning of the furnace cavity at least three times before vacuum preheating, thus creating an inherently safe high-purity atmosphere environment for the subsequent high-temperature reduction reaction. Specifically, the multiple cycles of "vacuuming-inert gas filling" can effectively remove trace amounts of oxygen remaining in the dead zones of the furnace cavity, pipe interfaces, and micropores of the graphite substrate disk based on the principle of exponential dilution, eliminating the risk of combustion and explosion caused by residual oxygen when H2 is introduced at high temperatures (especially above 1300°C). At the same time, the establishment of an extremely low oxygen background effectively inhibits the oxidation and etching reactions of the graphite substrate disk and SiC coating at high temperatures (such as C+O2→CO / CO2), completely protecting the stoichiometry and surface finish of the coating. This "replacement first, then heating" pretreatment strategy not only ensures the safety of the process, but also eliminates the competitive interference of oxidizing impurities on the H2 reduction reaction, ensuring that the reducing gas can efficiently decompose deposits such as AlN and GaN. This lays a clean atmospheric foundation for the thoroughness of the entire cleaning process and further extends the service life of the graphite substrate.

[0044] In the above embodiments, the inert gas includes N2, with a flow rate of 500 sccm-1500 sccm and a purity ≥99.9999%; the reducing gas includes H2, with a flow rate of 95 sccm-150 sccm and a purity ≥99.9999%; wherein in the high-temperature deep cleaning step, the volume ratio of N2 to H2 in the mixed gas is (5-15):1.

[0045] The above ratio ensures a sufficient supply of reducing agent to decompose Group III nitrides, while utilizing a large amount of N2 carrier gas to carry away the reaction products, thus ensuring the safety of the process. Of course, other inert gases besides N2 can be used, and other reducing gases besides H2 can also be used.

[0046] In the above embodiments, the diameter of the graphite substrate disk is 180mm-380mm, and the skirt length is 50mm-65mm.

[0047] In this embodiment, the cleaning method of this application is particularly suitable for graphite-based disks with deep skirt structures, specifically, for graphite-based disks with a disk diameter between 180mm and 380mm and a skirt length between 50mm and 65mm. This size range covers the current specifications of carrier disks for small and medium diameter Si-based GaN epitaxy. This invention, through a dynamic pressure-changing cleaning mechanism, can overcome the problem of gas replacement dead zones faced during the cleaning of such deep-skirt structures.

[0048] The technical solutions of the present invention will be described in detail below through specific embodiments. Example

[0049] This embodiment 1 provides a complete dry cleaning process for graphite-based disks used in silicon-based nitride epitaxy. The experimental subject is a graphite-based disk with a diameter of 213 mm and a skirt length of 51 mm (refer to...). Figure 3 Its specifications are 1×4 inches (i.e., it has one groove for supporting a 4-inch wafer), the groove depth is 1mm, the base thickness is 8mm, and the surface is covered with a dense SiC coating. For example... Figure 1 As shown, the graphite substrate disk cleaning method of this embodiment 1 includes the following steps performed in sequence: S1: Vacuum preheating and primary cleaning.

[0050] The graphite substrate disk to be cleaned is placed in a sealed furnace chamber, and the temperature inside the furnace chamber is raised from room temperature to a first temperature range of 200℃-400℃ under vacuum. In this embodiment 1, the temperature is preferably 360℃. During this period, inert gas is introduced into the furnace chamber and a pressure swing cleaning operation is performed.

[0051] Specifically, this step aims to remove physically adsorbed water and volatile organic compounds from the surface of the graphite substrate disk. First, the temperature is increased at a gentle rate of 1.0℃ / min to purge the original gas from the space, and a 1×10⁻⁶ temperature rise is established around 30℃. -2 The furnace was then subjected to a high vacuum environment (Tor). Subsequently, the temperature was increased to 360°C at a rate of 5°C / min. During this heating and holding phase, an "N2 pressure-switching cleaning operation" was initiated, controlling the process gas (N2) to be injected into the furnace cavity in laminar flow mode (Reynolds number Re≤2000, flow rate 2.5L / min). Simultaneously, a pressure circulation mechanism was implemented, rapidly increasing the furnace cavity pressure from vacuum to 3 Torr (half a filling cycle, as the upper limit pressure) within 6-7 seconds. The gas supply was then cut off, and full-speed evacuation was initiated, causing the pressure to drop back to 1×10⁻⁶ within 75-85 seconds. -2 Torr (half-cycle of pumping, used as the lower limit pressure), such as Figure 2 As shown. This cycle lasts for about 35 minutes. By utilizing the increased mean free path of molecules under low pressure, combined with the airflow disturbance generated by pressure pulsation, the desorption of surface-adsorbed impurities can be effectively enhanced.

[0052] S2: High-temperature deep cleaning.

[0053] The temperature inside the furnace chamber is gradually increased from the first temperature range to the second temperature range of 1300℃-1450℃, preferably 1400℃ in this embodiment 1. During this period, a mixture of inert gas and reducing gas is introduced into the furnace chamber, and optimized pressure swing cleaning operation is continuously performed.

[0054] Specifically, this step is the core reaction stage, utilizing a high-temperature coupled reducing atmosphere to decompose deep, stubborn deposits. When the temperature rises above 360℃, the process gas is switched to an N2 / H2 mixture, with a volume ratio controlled at 10:1. Subsequently, the temperature is increased at a preset rate (8℃ / min), sequentially passing through the 600℃, 1000℃, and 1100℃ nodes, ultimately reaching a high-temperature steady-state zone of 1400℃. During the temperature rise and within the 600℃-1100℃ range, the pressure transformer parameters are adjusted to "charge for 4-5 seconds / evacuate for 50-60 seconds" to improve mass transfer efficiency and complete the replacement of the furnace atmosphere. When the temperature stabilizes at a constant temperature of 1400℃±10℃, a deep pressure transformer cleaning process is performed for up to 390 minutes. In this crucial step, the pressure transformer parameters are further optimized to "charge for 3-4 seconds / evacuate for 40-50 seconds." This high-frequency, high-amplitude sawtooth pressure waveform (3Torr↔10) -2 Torr can generate a strong "breathing effect", forcing H2 molecules to overcome the diffusion resistance in the micropores and penetrate deep into the pits of the SiC coating to reduce and decompose Group III nitride deposits such as AlN and GaN into gaseous metal atoms (such as Ga vapor) or hydrides, and expel the reaction byproducts during the pumping process.

[0055] S3: Pressure cooling transition.

[0056] The temperature inside the furnace cavity is reduced from the second temperature range to a third temperature range of 800℃-950℃. In this embodiment 1, it is preferably reduced to 950℃. During this period, the supply of reducing gas is cut off, and only inert gas is introduced to maintain the pressure swing cleaning operation.

[0057] Specifically, this step aims to prevent the reverse adsorption of high-temperature gaseous products. First, the H2 supply is stopped, and only pure N2 is introduced, with the temperature reduced from 1400℃ to 950℃ at a rate of 8℃ / min. During this cooling range, the N2 pressure swing cleaning operation from step S1 is resumed and continued for 30 minutes. Through continuous pulsating of pure inert gas, any metal vapors that may have precipitated due to supersaturation during the cooling process are completely removed from the furnace chamber, preventing secondary sublimation and contamination of the graphite substrate surface.

[0058] S4: Vacuum and cooling termination.

[0059] When the temperature inside the furnace chamber drops to the third temperature range, stop the N2 supply. Then, maintain a vacuum environment in the furnace chamber and reduce the temperature inside the furnace chamber from the third temperature range to the fourth temperature range of 600℃-850℃ (preferably 850℃ in this embodiment 1). During this period, stop the gas supply and maintain the vacuum environment to cool down. When the temperature drops to 850℃, then fill with N2 to cool down to room temperature to complete the cleaning.

[0060] Specifically, this step utilizes a high vacuum environment to isolate oxygen and prevent high-temperature oxidation. During the cooling range of 950℃ to 850℃, gas filling is stopped, and the gas in the furnace cavity is expelled, ensuring the furnace cavity is at a temperature better than 5×10⁻⁶. -2 The high vacuum state of the Torr system prevents oxidation and etching of the graphite substrate from contact with trace amounts of oxygen at high temperatures, thus protecting the mirror-like finish of the substrate surface and the integrity of the SiC coating. Once the temperature drops below 850°C, high-purity N2 is introduced to atmospheric pressure, and the cooling rate is controlled to ≤15°C / min until the substrate reaches room temperature. Finally, the graphite substrate is removed, and the surface cleaning effect is inspected. If the appearance is uniform and free of residue, the cleaning is considered successful. Example

[0061] This Example 2 aims to demonstrate a rapid cleaning solution under a low-temperature range and a high-concentration reducing atmosphere, suitable for scenarios with thin deposits or high production cycle requirements. The object being treated is a medium-sized graphite-based disk with a disk diameter of 380 mm and a skirt length of 65 mm (i.e., the upper limit of the stated size range, to verify the cleaning capability for medium-sized graphite-based disks with deep skirts). Figure 1 As shown, the graphite substrate disk cleaning method of this embodiment 2 includes the following steps performed in sequence: S1: Vacuum preheating and primary cleaning.

[0062] The graphite substrate to be cleaned was placed in a sealed furnace chamber, and the chamber was evacuated for leak testing. Then, under vacuum, the furnace temperature was rapidly increased from room temperature to a first temperature of 200°C at a rate of 5°C / min and maintained stable. During this period, N2 was introduced and a variable pressure cleaning operation was performed, controlling the inflation time to 3 seconds and the evacuation time to 40 seconds, with a total cleaning cycle of 20 minutes to quickly remove adsorbed moisture from the surface.

[0063] S2: High-temperature deep cleaning.

[0064] The temperature inside the furnace chamber is gradually increased from 200℃ to a second temperature of 1300℃. During this process, a mixture of N2 and H2 gas is introduced, with the volume ratio of N2 to H2 controlled at 7:1. The upper limit pressure of the pressure swing cleaning operation is controlled at 2.5 Torr, and the lower limit pressure is 5 × 10⁻⁶. -2 Torr, with an inflation time of 3 seconds and an evacuation time of 40 seconds. The sediment was continuously washed at a constant temperature of 1300℃ for 120 minutes, utilizing high-concentration H2 to achieve reduction and decomposition of the sediment with low energy consumption.

[0065] S3: Pressure cooling transition.

[0066] Cut off the H2 supply and introduce only N2. Rapidly reduce the temperature inside the furnace chamber from 1300°C to a third temperature of 800°C at a cooling rate of 10°C / min. During this process, maintain the same N2 flow rate and variable pressure cleaning frequency as in step S2, using N2 pulses to quickly remove reaction residues.

[0067] S4: Vacuum and cooling termination.

[0068] When the temperature drops to 800℃, stop the N2 supply, but continue evacuation to maintain the pressure inside the furnace chamber at the ultimate vacuum. Continue to lower the temperature to a fourth temperature of 600℃ at a rate of 10℃ / min. Then stop evacuation, introduce N2 to atmospheric pressure, and perform cooling treatment until the furnace chamber temperature drops to room temperature. Remove the graphite substrate to complete the cleaning. Example

[0069] This embodiment 3 aims to demonstrate a deep cleaning solution using a low-concentration reducing atmosphere in the extreme high-temperature range. It is suitable for stubborn residues with extremely thick deposits or complex compositions, while maximizing the protection of the silicon carbide coating. For example... Figure 1 As shown, the graphite substrate disk cleaning method of this embodiment 3 includes the following steps performed in sequence: S1: Vacuum preheating and primary cleaning.

[0070] The graphite substrate disk to be cleaned was placed in a sealed furnace chamber. Under vacuum, the temperature inside the furnace chamber was raised from room temperature to a first temperature of 400°C at a slow rate of 0.5°C / min and maintained stable. During this period, N2 was introduced and a pressure swing cleaning operation was performed, with the gas filling time controlled at 8 seconds and the gas extraction time at 90 seconds, and the cleaning cycle repeated for 45 minutes to ensure that the adsorbed impurities in the deep micro-pits were fully desorbed.

[0071] S2: High-temperature deep cleaning.

[0072] The temperature inside the furnace chamber is gradually increased from 400℃ to a second temperature of 1450℃. During this process, a mixture of N2 and H2 gas is introduced, maintaining a N2:H2 volume ratio of 15:1 (i.e., a low-reducing atmosphere) to prevent over-corrosion and maintain the pressure swing cleaning operation. The upper pressure limit is controlled at 3.5 Torr, and the lower pressure limit is 1.5 × 10⁻⁶. -2 The Torr system has an inflation time of 8 seconds and a deflation time of 90 seconds. It is maintained at an extreme high temperature of 1450℃ for 400 minutes, utilizing prolonged high-temperature pyrolysis combined with trace amounts of H2 reduction to thoroughly remove stubborn deposits.

[0073] S3: Pressure cooling transition.

[0074] Cut off the H2 supply and introduce only N2. Slowly reduce the furnace temperature from 1450℃ to the third temperature range of 950℃ at a rate of 5℃ / min. During this process, maintain the pressure swing cleaning operation to ensure that gaseous metal atoms do not undergo secondary condensation at high temperatures.

[0075] S4: Vacuum and cooling termination.

[0076] Once the temperature drops to 950℃, stop the ventilation and continue evacuation to maintain a high vacuum. Allow the temperature to naturally decrease to a fourth temperature of 850℃ at a rate of 5℃ / min. Then, purge with N2 to atmospheric pressure and allow for cooling, slowly reducing the temperature to room temperature to complete the cleaning process. Example

[0077] This embodiment 4 provides a comprehensive optimization scheme that balances cleaning efficiency and energy consumption. For example... Figure 1 As shown, the graphite substrate disk cleaning method of this embodiment 4 includes the following steps performed in sequence: S1: Vacuum preheating and primary cleaning.

[0078] The graphite substrate to be cleaned is placed in a sealed furnace chamber. The furnace temperature is raised to a first temperature of 300°C at a rate of 3°C / min under vacuum. N2 is introduced for pressure cleaning, with an inflation time of 5 seconds and a evacuation time of 60 seconds, for a total of 30 minutes.

[0079] S2: High-temperature deep cleaning.

[0080] The temperature inside the furnace chamber is increased to a second temperature of 1380℃ at a rate of 5℃ / min. A mixture of N2 and H2 gas is introduced, with the volume ratio of N2 to H2 controlled at 10:1. A pressure swing cleaning operation is performed, with the upper limit pressure set at 3.0 Torr and the lower limit pressure at 1.0 × 10⁻⁶. -2 Torr, inflation time 5 seconds, deflation time 60 seconds. Constant temperature cleaning at 1380℃ for 240 minutes.

[0081] S3: Pressure cooling transition.

[0082] Cut off H2 while maintaining N2 flow. Reduce the temperature to a third temperature of 900°C at a rate of 8°C / min, while continuously performing transformer purging.

[0083] S4: Vacuum and cooling termination.

[0084] When the temperature dropped to 900℃, the gas supply was stopped, and the temperature was further reduced from 900℃ to a fourth temperature of 800℃ under vacuum. Subsequently, it was cooled to room temperature by purging with N2. Inspection revealed that the graphite substrate surface was as smooth as new under these process conditions, and the SiC coating showed no signs of damage.

[0085] Comparative ratio and verification of beneficial effects To further verify the actual technical effect of the graphite-based disk dry cleaning method described in this invention, especially to verify its effect on improving the growth quality of epitaxial wafers, the present invention designed the following comparative experiment.

[0086] Comparative Example 1 A graphite substrate with the same specifications as in Example 1, but which has been used under the same process, has a deposited contamination layer on its surface, and has not been treated by the dry cleaning process of this invention, is selected.

[0087] Example Group (Example 1) A graphite substrate disk with the same level of contamination as Comparative Example 1, but treated with the cleaning process described in Example 1 of this invention, was selected.

[0088] Test Method: Using identical silicon-based nitride MOCVD epitaxial process parameters, one 4-inch epitaxial wafer was grown on the graphite substrate disk of Comparative Example 1 and Example Group (Example 1), respectively. Subsequently, the grown wafers were subjected to full-wafer photoluminescence (PL) scanning using wafer testing equipment to collect and calculate the in-plane distribution data of the following core parameters: dominant wavelength (WLD), PL intensity (INT (Integrated Intensity), full width at half maximum (HW), and wafer curvature (BOW).

[0089] The full-wafer scan data of the two sets of wafers were statistically analyzed. After removing invalid points at the edges, the comparison results of the core parameters are shown in Table 1.

[0090]

[0091] Combining the data in Table 1 and Figures 4 to 7 Further analysis was conducted on the above experimental results. The results are as follows: Stereomicroscopy observation (see Figure 4 After processing using the process described in Example 1, the deposits adhering to the surface of the graphite substrate disk (see...) Figure 4 (a) has been effectively removed, showing a significantly clean state (see Figure 4 (b)). Stereoscopic examination results showed that the coating surface had no peeling, no new cracks, and no excessive etching marks, confirming that the process has a non-destructive cleaning characteristic for graphite-based disk coatings.

[0092] Thermal field uniformity restoration (see) Figure 5 Comparative Example 1 shows a wide-amplitude multi-peak distribution of the dominant wavelength (STD=19.34nm), indicating that the deposits cause uneven thermal resistance and distortion of the thermal field distribution; while Example 1 converges to an extremely narrow Gaussian single peak (STD=1.33nm, optimization 93.1%), confirming that the process of this application completely removes the impurity layer and restores the atomic-level composition control capability of the substrate.

[0093] A leap in crystal quality (see Figure 6 The PL mapping of Comparative Example 1 shows large areas of disordered defects, indicating a high density of interface defects; while Example 1 shows uniform high brightness throughout, with an average intensity increase of 32.6%. This result confirms that the surface cleanliness of the substrate has been restored to a brand-new level, effectively suppressing dislocation proliferation at the epitaxial interface.

[0094] Non-destructive cleaning and stress relief (see) Figure 7 The radial warpage of Comparative Example 1 is extremely high (up to approximately 750 μm), and decreases from the center to the edge, indicating highly uneven radial deformation. In contrast, the curve of Example 1 is flat and zero (average value of only 12.15 μm). This demonstrates that this application removes stubborn deposits without damaging the SiC coating, ensuring microscopic smoothness and ideal stress release.

[0095] Therefore, the periodic voltage transformation and high-temperature chemical reaction synergistic cleaning method provided in this application can restore the performance of graphite substrate disks to near-new levels. By significantly improving the optical uniformity and physical flatness of epitaxial wafers, it significantly improves the yield of high-end LED chips and power devices, and has significant industrial applicability.

[0096] In summary, this invention utilizes the synergistic effect of the "breathing effect" generated by pressure pulses and high-temperature chemical reduction to force the reactive gas deep into the micro-pits of the SiC coating on the graphite-based disk. This efficiently decomposes strongly adhering deposits such as AlN and GaN, which are then discharged with the airflow. This method cleans the deposits on the graphite tray surface while avoiding damage to the silicon carbide coating. The dry cleaning method for graphite-based disks in this invention mainly employs a dynamic pressure field coupled with a high-temperature chemical reaction, which can thoroughly remove stubborn deposits generated in silicon-based nitride epitaxial processes. Moreover, the method of this application not only has a rigorous operational logic, thorough cleaning, and no damage to the coating, but also greatly extends the service life of the graphite-based disk (up to 260 heats or more). Therefore, the dry cleaning method for graphite-based disks in this application solves the problems of coating damage, micropore residue, and high maintenance costs associated with existing cleaning methods in silicon-based nitride epitaxial technology.

[0097] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0098] The above descriptions are merely embodiments of this application, which enable those skilled in the art to understand and implement this application. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Claims

1. A dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy, characterized in that, Includes the following steps: Vacuum preheating and primary cleaning: The graphite substrate is placed in a sealed furnace cavity, and the temperature inside the furnace cavity is raised to the first temperature range under vacuum. During this period, inert gas is introduced into the furnace cavity and a pressure swing cleaning operation is performed. High-temperature deep cleaning: The temperature inside the furnace cavity is raised from the first temperature range to the second temperature range. During this period, a mixture of inert gas and reducing gas is introduced into the furnace cavity, and the pressure swing cleaning operation is continuously performed. Pressurized cooling transition: The temperature inside the furnace cavity is cooled from the second temperature range to the third temperature range. During this period, the supply of the reducing gas is cut off, and only the inert gas is introduced while the pressure swing cleaning operation is maintained. Vacuum and cooling termination: When the temperature inside the furnace chamber drops to the third temperature range, the inert gas supply is stopped, and then the furnace chamber is kept in a vacuum environment. The temperature inside the furnace chamber is then cooled from the third temperature range to the fourth temperature range. Subsequently, inert gas is introduced into the furnace chamber and cooled to room temperature.

2. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, The variable pressure cleaning operation includes cyclically performing air filling and air extraction steps, so that the pressure in the furnace cavity fluctuates alternately between a preset upper limit pressure and a lower limit pressure, wherein the upper limit pressure is 0.5 Torr-7 Torr and the lower limit pressure is 0.01 Torr-0.49 Torr. The duration of the air filling step is 3s-8s and the duration of the air extraction step is 40s-90s.

3. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, The first temperature range is 200℃-400℃, the second temperature range is 1300℃-1450℃, the third temperature range is 800℃-950℃, and the fourth temperature range is 600℃-850℃.

4. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, The vacuum preheating and primary cleaning steps further include: The temperature inside the furnace chamber was raised from room temperature to 30℃-50℃ while a vacuum process was performed simultaneously. Vacuuming was performed until the pressure inside the furnace reached 10. -1 Torr-10 -2 Torr, and raise the temperature to the target temperature within the first temperature range at a rate of 0.5℃ / min-5℃ / min. During this heating process, the pressure swing cleaning operation of the inert gas is initiated and maintained.

5. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, The high-temperature deep cleaning step further includes: The temperature inside the furnace cavity is gradually increased from the first temperature range to the target temperature in the second temperature range at a heating rate of 3℃ / min-15℃ / min. Maintain a constant temperature at the target temperature for 120 min-400 min; The pressure swing cleaning operation of the mixed gas is continuously performed throughout the heating and isothermal processes.

6. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, The pressurized cooling transition step further includes: The temperature inside the furnace cavity is cooled from the second temperature range to the third temperature range at a cooling rate of 5℃ / min-10℃ / min. During this period, the supply of the reducing gas is cut off, and only the inert gas is introduced. During this cooling period, the same inert gas flow rate and variable pressure cleaning operating parameters as in the high temperature deep cleaning step are maintained.

7. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, The vacuum and cooling termination step further includes: The temperature inside the furnace cavity is reduced from the third temperature range to the fourth temperature range at a cooling rate of 5℃ / min-10℃ / min. During this period, gas filling is stopped and gas is discharged to maintain the vacuum environment of the furnace cavity. After the temperature inside the furnace chamber falls below the lower limit of the fourth temperature range, inert gas is introduced into the furnace chamber to atmospheric pressure, and the temperature inside the furnace chamber is reduced to room temperature.

8. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, Before performing the vacuum preheating and primary cleaning, the furnace cavity is cleaned with inert gas for no less than three times to reduce the oxygen content in the furnace cavity to below the safe threshold.

9. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to any one of claims 1-8, characterized in that, The inert gas includes N2, with a flow rate of 500 sccm-1500 sccm and a purity ≥99.9999%; the reducing gas includes H2, with a flow rate of 95 sccm-150 sccm and a purity ≥99.9999%; wherein, in the high-temperature deep cleaning step, the volume ratio of N2 to H2 in the mixed gas is (5-15):

1.

10. The dry cleaning method for graphite-based disks used in silicon-based nitride epitaxy according to claim 1, characterized in that, The diameter of the graphite substrate disk is 180mm-380mm, and the skirt length is 50mm-65mm.

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